Polycythemia vera, essential thrombocythemia, and idiopathic myelofibrosis are clonal myeloproliferative disorders arising from a multipotent progenitor. The loss of heterozygosity (LOH) on the short arm of chromosome 9 (9pLOH) in myeloproliferative disorders suggests that 9p harbors a mutation that contributes to the cause of clonal expansion of hematopoietic cells in these diseases. We performed microsatellite mapping of the 9pLOH region and DNA sequencing in 244 patients with myeloproliferative disorders (128 with polycythemia vera, 93 with essential thrombocythemia, and 23 with idiopathic myelofibrosis). Microsatellite mapping identified a 9pLOH region that included the Janus kinase 2 (JAK2) gene. In patients with 9pLOH, JAK2 had a homozygous G→T transversion, causing phenylalanine to be substituted for valine at position 617 of JAK2 (V617F). All 51 patients with 9pLOH had the V617F mutation. Of 193 patients without 9pLOH, 66 were heterozygous for V617F and 127 did not have the mutation. The frequency of V617F was 65 percent among patients with polycythemia vera (83 of 128), 57 percent among patients with idiopathic myelofibrosis (13 of 23), and 23 percent among patients with essential thrombocythemia (21 of 93). V617F is a somatic mutation present in hematopoietic cells. Mitotic recombination probably causes both 9pLOH and the transition from heterozygosity to homozygosity for V617F. Genetic evidence and in vitro functional studies indicate that V617F gives hematopoietic precursors proliferative and survival advantages. Patients with the V617F mutation had a significantly longer duration of disease and a higher rate of complications (fibrosis, hemorrhage, and thrombosis) and treatment with cytoreductive therapy than patients with wild-type JAK2. A high proportion of patients with myeloproliferative disorders carry a dominant gain-of-function mutation of JAK2.

Nephropathy associated with the polyomavirus type BK (BKV) nephropathy has emerged as a cause of allograft failure linked to immunosuppressive regimens containing tacrolimus or mycophenolate mofetil. The presence of viral inclusions, known as “decoy cells,” in urine and the presence of BKV DNA in plasma have been proposed as markers for the replication of BKV and associated nephropathy, but data from prospective studies have been lacking. In a prospective, single-center study, we followed 78 renal-transplant recipients who were receiving immunosuppressive therapy that included tacrolimus (37 patients) or mycophenolate mofetil (41 patients). Urine was tested for the presence of decoy cells at routine visits. BKV DNA was measured 3, 6, and 12 months after transplantation and whenever decoy cells were detected. The viral load in plasma was quantified with the use of a real-time polymerase-chain-reaction method. Renal biopsy was performed if allograft function deteriorated. Twenty-three patients had decoy-cell shedding a median of 16 weeks after transplantation (range, 2 to 69), 10 patients had BKV viremia at a median of 23 weeks (range, 4 to 73), and 5 had BKV nephropathy at a median of 28 weeks (range, 8 to 86). Kaplan–Meier estimates of the probability of decoy-cell shedding, viremia, and nephropathy were 30 percent (95 percent confidence interval, 20 to 40 percent), 13 percent (95 percent confidence interval, 5 to 21 percent), and 8 percent (95 percent confidence interval, 1 to 15 percent), respectively. Antirejection treatment, particularly with corticosteroids, was associated with BKV replication and nephropathy. The viral load in plasma was higher in patients with BKV nephropathy than in those without nephropathy (P<0.001 by the Mann–Whitney test). BKV antibodies were detected in 77 percent of the 78 patients before transplantation, including 4 of 5 with BKV nephropathy. BKV nephropathy in renal-transplant recipients represents a secondary infection associated with rejection and its treatment in most cases and could be monitored by measuring the viral load in plasma.

Patients with acute myeloid leukemia (AML) often reach complete remission, but relapse rates remain high. Next-generation sequencing enables the detection of molecular minimal residual disease in virtually every patient, but its clinical value for the prediction of relapse has yet to be established.

It is uncertain whether mortality rates among patients who have undergone bone marrow transplantation return to the level of the mortality rates of the general population. We analyzed the characteristics of 6691 patients listed in the International Bone Marrow Transplant Registry. All the patients were free of their original disease two years after allogeneic bone marrow transplantation. Mortality rates in this cohort were compared with those of an age-, sex-, and nationality-matched general population. Cox proportional-hazards regression was used to identify risk factors for death more than two years after transplantation (late death). Among patients who were free of disease two years after transplantation, the probability of living for five more years was 89 percent (95 percent confidence interval, 88 to 90 percent). Among patients who underwent transplantation for aplastic anemia, the risk of death by the sixth year after transplantation did not differ significantly from that of a normal population. Mortality remained significantly higher than normal throughout the study among patients who underwent transplantation for acute lymphoblastic leukemia or chronic myelogenous leukemia and through the ninth year among those who underwent transplantation for acute myelogenous leukemia. Recurrent leukemia was the chief cause of death among patients who received a transplant for leukemia, whereas chronic graft-versus-host disease was the chief cause among those who received a transplant for aplastic anemia. Advanced, long-standing disease before transplantation and active chronic graft-versus-host disease were important risk factors for late death. In patients who receive an allogeneic bone marrow transplant as treatment for acute myelogenous or lymphoblastic leukemia, chronic myelogenous leukemia, or aplastic anemia and who are free of their original disease two years later, the disease is probably cured. However, for many years after transplantation, the mortality among these patients is higher than that in a normal population.

Acute graft‐versus‐host disease (GVHD) severity is graded by pattern of organ involvement and clinical performance status using a system introduced by Glucksberg and colleagues 21 years ago. We examined how well Glucksberg grade predicted transplant outcome and constructed a Severity Index not requiring subjective assessment of performance in 2881 adults receiving an HLA‐identical sibling T‐cell‐depleted (n = 752) or non‐T‐cell‐depleted (n = 2129) bone marrow transplant for leukaemia between 1986 and 1992. Relative risks (RR) of relapse, treatment‐related mortality (TRM) and treatment failure (TF) (relapse or death) were calculated for patients with Glucksberg Grade I, II or III/IV acute GVHD versus those without acute GVHD and for patients with distinct patterns of organ involvement regardless of Glucksberg grade. Using data for non‐T‐cell‐depleted transplants, a Severity Index was developed grouping patients with patterns of organ involvement associated with similar risks of TRM and TF. Higher Glucksberg grade predicted poorer outcome; however, patients with the same grade but different patterns of skin, liver or gut involvement often had significantly different outcomes. The revised Severity Index groups patients in four categories, A–D. Compared to patients without acute GVHD, RRs (95% confidence interval) of TF were 0.85 (0.69, 1.05) for patients with Index A, 1.21 (1.02, 1.43) with B, 2.19 (1.78, 2.71) with C, and 5.69 (4.57, 7.08) with D. Prognostic utility of the Index was tested in patients receiving T‐cell‐depleted transplants; similar RRs of TF were observed. An acute GVHD Severity Index is proposed to enhance design and interpretation of clinical trials in the current era of allogeneic blood and bone marrow transplantation.

Myeloproliferative neoplasms (MPNs) are a group of clonal disorders characterized by aberrant hematopoietic proliferation and an increased tendency toward leukemic transformation. We used targeted next-generation sequencing (NGS) of 104 genes to detect somatic mutations in a cohort of 197 MPN patients and followed clonal evolution and the impact on clinical outcome. Mutations in calreticulin (CALR) were detected using a sensitive allele-specific polymerase chain reaction. We observed somatic mutations in 90% of patients, and 37% carried somatic mutations other than JAK2 V617F and CALR. The presence of 2 or more somatic mutations significantly reduced overall survival and increased the risk of transformation into acute myeloid leukemia. In particular, somatic mutations with loss of heterozygosity in TP53 were strongly associated with leukemic transformation. We used NGS to follow and quantitate somatic mutations in serial samples from MPN patients. Surprisingly, the number of mutations between early and late patient samples did not significantly change, and during a total follow-up of 133 patient years, only 2 new mutations appeared, suggesting that the mutation rate in MPN is rather low. Our data show that comprehensive mutational screening at diagnosis and during follow-up has considerable potential to identify patients at high risk of disease progression. Key Points The total number of somatic mutations was inversely correlated with survival and risk of leukemic transformation in MPN. The great majority of somatic mutations were already present at MPN diagnosis, and very few new mutations were detected during follow-up.